U.S. patent application number 11/592073 was filed with the patent office on 2007-05-03 for organic light emitting display device and method of fabricating the same.
Invention is credited to Hyun-Eok Shin.
Application Number | 20070096614 11/592073 |
Document ID | / |
Family ID | 37867601 |
Filed Date | 2007-05-03 |
United States Patent
Application |
20070096614 |
Kind Code |
A1 |
Shin; Hyun-Eok |
May 3, 2007 |
Organic light emitting display device and method of fabricating the
same
Abstract
An organic light emitting display device including a first
electrode that has a three layer structure, improved adhesion, and
is simple to fabricate, and a method of fabricating the same, are
provided. The organic light emitting display device includes: a
substrate; a first electrode disposed on the substrate, the first
electrode comprising a first metal layer including Mo or an Mo
alloy, a second metal layer disposed on the first metal layer and
including Ag or an Ag alloy, and a third metal layer disposed on
the second metal layer and including a transparent conductive oxide
layer; an organic layer disposed on the first electrode and
including an organic emission layer; and a second electrode
disposed on the organic layer.
Inventors: |
Shin; Hyun-Eok; (Suwon-si,
KR) |
Correspondence
Address: |
CHRISTIE, PARKER & HALE, LLP
PO BOX 7068
PASADENA
CA
91109-7068
US
|
Family ID: |
37867601 |
Appl. No.: |
11/592073 |
Filed: |
November 1, 2006 |
Current U.S.
Class: |
313/112 ;
313/504; 315/169.3 |
Current CPC
Class: |
H01L 51/105 20130101;
H01L 2251/305 20130101; H01L 2251/5315 20130101; H01L 51/5218
20130101 |
Class at
Publication: |
313/112 ;
313/504; 315/169.3 |
International
Class: |
H01J 63/04 20060101
H01J063/04; H01J 5/16 20060101 H01J005/16; H01K 1/26 20060101
H01K001/26; G09G 3/10 20060101 G09G003/10; H01K 1/30 20060101
H01K001/30; H01J 1/62 20060101 H01J001/62; H01J 61/40 20060101
H01J061/40 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 2, 2005 |
KR |
10-2005-0104508 |
Claims
1. An organic light emitting display device, comprising: a
substrate; a first electrode disposed on the substrate, the first
electrode comprising a first metal layer including molybdenum (Mo)
or an Mo alloy, a second metal layer disposed on the first metal
layer and including silver (Ag) or an Ag alloy, and a third metal
layer disposed on the second metal layer and including a
transparent conductive oxide layer; an organic layer disposed on
the first electrode and including an organic emission layer; and a
second electrode disposed on the organic layer.
2. The organic light emitting display device according to claim 1,
wherein the first metal layer has a thickness of 50 .ANG. to 200
.ANG..
3. The organic light emitting display device according to claim 1,
wherein the Mo alloy is a molybdenum tungsten (MoW) alloy.
4. The organic light emitting display device according to claim 2,
wherein the second metal layer has a thickness of 900 .ANG. to 2000
.ANG..
5. The organic light emitting display device according to claim 1,
wherein the Ag alloy comprises at least one of samarium (Sm),
copper (Cu), terbium (Tb), Mo or tungsten (W).
6. The organic light emitting display device according to claim 1,
wherein the third metal layer has a thickness of 50 .ANG. to 100
.ANG..
7. The organic light emitting display device according to claim 1,
wherein the transparent conductive oxide layer comprises indium tin
oxide (ITO) or indium zinc oxide (IZO).
8. An electronic device comprising a body containing electronics;
and the organic light emitting display device according to claim 1
mounted on the body.
9. A method of fabricating an organic light emitting display
device, comprising: forming a first electrode on a substrate, the
first electrode comprising a first metal layer including molybdenum
(Mo) or an Mo alloy, a second metal layer including silver (Ag) or
an Ag alloy, and a third metal layer including a transparent
conductive oxide layer; forming an organic layer including an
organic emission layer on the first electrode; and forming a second
electrode on the organic layer.
10. The method according to claim 9, wherein forming the first
electrode further comprises blanket-etching the first electrode
using wet-etching.
11. The method according to claim 10, wherein the wet-etching uses
an etchant including phosphoric acid, acetic acid or nitric
acid.
12. The method according to claim 9, wherein the first metal layer
is formed to a thickness of 50 .ANG. to 200 .ANG..
13. The method according to claim 9, wherein the Mo alloy is a
molybdenum tungsten (MoW) alloy.
14. The method according to claim 9, wherein the second metal layer
is formed to a thickness of 900 .ANG. to 2000 .ANG..
15. The method according to claim 9, wherein the Ag alloy comprises
at least one of samarium (Sm), copper (Cu), terbium (Tb), Mo or
tungsten (W).
16. The method according to claim 9, wherein the third metal layer
is formed to a thickness of 50 .ANG. to 100 .ANG..
17. The method according to claim 9, wherein the transparent
conductive oxide layer comprises indium tin oxide (ITO) or indium
zinc oxide (IZO).
18. The method according to claim 9, further comprising preparing
the substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2005-0104508, filed Nov. 2, 2005
in the Korean Intellectual Property Office, the entire content of
which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an organic light emitting
display device and a method of fabricating the same, and more
particularly, to an organic light emitting display device that
includes a first electrode having a first metal layer, a second
metal layer, and a third metal layer including a transparent
conductive oxide layer, and a method of fabricating the same.
[0004] 2. Description of the Related Art
[0005] In general, an organic light emitting display device
includes a first electrode, an organic layer disposed on the first
electrode and having an organic emission layer, and a second
electrode disposed on the organic layer. In the organic light
emitting display device, when a voltage is applied between the
first and second electrodes, holes are injected from the first
electrode into the organic layer, and electrons are injected from
the second electrode into the organic layer. The holes and
electrons injected into the organic layer are recombined in the
organic emission layer and form excitons. When the excitons
transition from an excited state to a ground state, light is
emitted.
[0006] In such an organic light emitting display device, the first
electrode is a reflection type, i.e., is formed to reflect light,
and the second electrode is a transmission type, i.e., is formed to
transmit light. Thus, a top-emission organic light emitting display
device that emits light from the organic emission layer toward the
second electrode may be fabricated.
[0007] Compared to widely commercialized liquid crystal displays
(LCDs), the organic light emitting display device, an active
emissive display device, has advantages of wide viewing angle, high
picture quality, and motion picture display capability due to a
30,000 times fast response speed. The organic light emitting
display device has a stacked structure having enhanced luminous
efficiency due to increased recombination of electrons and
holes.
[0008] In the organic light emitting display devices, while a
conductive material having an excellent reflection property and an
appropriate work function is suitable for the reflection-type first
electrode, it appears that no single applicable material has both
of these properties. Accordingly, the reflection-type first
electrode may be formed in a multi-layer structure.
[0009] FIG. 1 is a schematic cross-sectional view illustrating a
method of fabricating a conventional organic light emitting display
device including a reflection-type first electrode.
[0010] Referring to FIG. 1, a substrate 100 on which a reflective
layer 110a and a transparent conductive layer 110b are sequentially
stacked is provided. A thin film transistor and a capacitor may be
included between the substrate 100 and the reflective layer
110a.
[0011] Here, the reflective layer 110a may include aluminum (Al)
which has an excellent reflection property, and the transparent
conductive layer 110b may be formed of indium tin oxide (ITO) or
indium zinc oxide (IZO) which has a high work function.
[0012] Subsequently, a photoresist pattern is formed on the
transparent conductive layer 110b, and the transparent conductive
layer 110b and the reflective layer 110a are sequentially etched
using the photoresist pattern as a mask. After etching, the
photoresist pattern is removed using a stripping solution so as to
complete a first electrode 110 including the reflective layer 110a
and the transparent conductive layer
[0013] Then, an organic layer 120 including an organic emission
layer is formed on the first electrode 110, and a second electrode
130 is formed on the organic layer, thereby completing an organic
light emitting display device.
[0014] However, Al and ITO, which are used respectively for a
reflective layer and a transparent conductive layer in a first
electrode of a conventional organic light emitting display device,
are impossible or extremely difficult to blanket-etch due to a
galvanic effect, and thus a fabrication process of the organic
light emitting display device is complicated. Also, since silver
(Ag), which can be blanket-etched along with ITO and has an
excellent reflection property, does not adhere well to a
planarization layer, a very gentle cleaning process is performed
and many particles remain, which is a leading cause of dark pixel
defects.
SUMMARY OF THE INVENTION
[0015] The present invention, in one embodiment, provides an
organic light emitting display device and a method of fabricating
the same, in which a first electrode has improved reflectivity and
adhesion to a planarization layer due to a modified composition and
structure, and has a simple fabrication process.
[0016] According to one aspect of the present invention, an organic
light emitting display device includes: a substrate; a first
electrode disposed on the substrate, the first electrode including
a first metal layer including molybdenum (Mo) or an Mo alloy, a
second metal layer disposed on the first metal layer and including
silver (Ag) or an Ag alloy, and a third metal layer disposed on the
second metal layer and including a transparent conductive oxide
layer; an organic layer disposed on the first electrode and
including an organic emission layer; and a second electrode
disposed on the organic layer.
[0017] According to another aspect of the present invention, a
method of fabricating an organic light emitting display device
includes: forming a first electrode on a substrate, the first
electrode including a first metal layer including Mo or an Mo
alloy, a second metal layer including Ag or an Ag alloy, and a
third metal layer including a transparent conductive oxide layer;
forming an organic layer including an organic emission layer on the
first electrode; and forming a second electrode on the organic
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above and other features of the present invention will
be described in reference to certain exemplary embodiments thereof
with reference to the attached drawings in which:
[0019] FIG. 1 is a schematic cross-sectional view illustrating a
method of fabricating a conventional organic light emitting display
device including a reflection-type first electrode;
[0020] FIG. 2 is a cross-sectional view illustrating an organic
light emitting display device according to an exemplary embodiment
of the present invention;
[0021] FIG. 3 is a portable terminal which is an electronic device
using an organic light emitting display device according to an
exemplary embodiment of the present invention;
[0022] FIG. 4A illustrates photographs of a peeling off phenomenon
occurring between a first electrode and a substrate in Comparative
Exemplary Embodiment 1;
[0023] FIG. 4B illustrates a photograph of adhesion of a first
electrode to a substrate according to Exemplary Embodiment 1;
and
[0024] FIG. 5 illustrates photographs of dark pixel defects caused
by particles of an organic light emitting display device in
Comparative Exemplary Embodiment 1.
DETAILED DESCRIPTION
[0025] The present invention will now be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments of the present invention are shown. In the
drawings, the thicknesses of layers and regions are exaggerated for
clarity. The same reference numerals are used to denote the same
elements throughout the specification.
[0026] FIG. 2 is a cross-sectional view illustrating an organic
light emitting display device (which may also be referred as an
organic light emitting diode (OLED) display) according to an
exemplary embodiment of the present invention.
[0027] Referring to FIG. 2, a buffer layer 210 is formed on a
substrate 200 formed of glass or plastic. A semiconductor layer 220
having source and drain regions 220a and 220b and a channel region
220c is formed on the buffer layer 210.
[0028] Here, the buffer layer 210 may be a silicon oxide layer, a
silicon nitride layer, a silicon oxynitride layer or a multi-layer
thereof. Also, the semiconductor layer 220 may be formed of
polycrystalline silicon or single crystal silicon crystallized from
amorphous silicon.
[0029] A gate insulating layer 230 is formed on substantially the
entire surface of the substrate having the semiconductor layer 220.
A gate electrode 240 is formed at a certain region corresponding to
the semiconductor layer 220 on the gate insulating layer 230.
[0030] The gate insulating layer 230 may be a silicon oxide layer,
a silicon nitride layer, a silicon oxynitride layer, or a
multi-layer thereof. The gate electrode 240 may be formed of one
selected from the group consisting of aluminum (Al), an Al alloy,
Molybdenum (Mo), and an Mo alloy. In one embodiment, the gate
electrode 240 is formed of a molybdenum-tungsten (MoW) alloy.
[0031] Then, an interlayer insulating layer 250 is formed on
substantially the entire surface of the substrate having the gate
electrode 240. The interlayer insulating layer 250 may be a silicon
nitride layer or a silicon oxide layer.
[0032] The interlayer insulating layer 250 and the gate insulating
layer 230 are etched so as to form contact holes 255a and 255b
exposing portions of the source and drain regions 220a and
220b.
[0033] Then, source and drain electrodes 260a and 260b electrically
connected to the source and drain regions 220a and 220b through the
contact holes 255a and 255b are formed. The source and drain
electrodes 260a and 260b are formed of a low-resistance material to
reduce interconnection resistance, for example, Mo, W, titanium
(Ti) or Al.
[0034] A planarization layer 270 is formed on substantially the
entire surface of the substrate including the source and drain
electrodes 260a and 260b. The planarization layer 270 may be formed
of polyimide, benzocyclobutene series resin or acrylate.
[0035] Subsequently, the planarization layer 270 is etched, thereby
forming a via hole 275 exposing a portion of the drain electrode
260b. First metal layer, second metal layer and third metal layer
280a, 280b and 280c are sequentially stacked to be electrically
connected to the drain electrode 260b through the via hole 275.
[0036] Here, the first metal layer 280a includes Mo or an Mo alloy
with excellent adhesion to the planarization layer 270, and the Mo
ally may be an MoW alloy. In one embodiment, the tungsten content
of the MoW alloy may be 10 to 35%. The first metal layer 280a may
be formed by sputtering. Also, the thickness of the first metal
layer 280a may be 5 .ANG. to 200 .ANG. (0.0005 .mu.m to 0.02
.mu.m). In one embodiment, when the thickness is less than 5 .ANG.,
the first metal layer cannot be evenly formed on the planarization
layer 270, and when the thickness is more than 200 .ANG., its
adhesion to the planarization layer 270 decreases due to the stress
of Mo itself.
[0037] Additionally, the second metal layer 280b includes Ag or an
Ag alloy with excellent reflectivity, and the Ag alloy may include
one or more of samarium (Sm), copper (Cu), terbium (Tb), molybdenum
(Mo) and tungsten (W). The second metal layer 280b may be formed by
sputtering. Also, the thickness of the second metal layer 280b may
be 900 .ANG. to 2000 .ANG. (0.09 .mu.m to 0.2 .mu.m). In one
embodiment, when the thickness is less than 900 .ANG., the second
metal layer partially transmits light so that it cannot effectively
work as a reflective layer, and when the thickness is more than
2000 .ANG., fabrication cost and process time increase, which is
not preferable.
[0038] Also, the third metal layer 280c may be a transparent
conductive oxide layer having a low work function, and the
transparent conductive oxide layer may be formed of ITO or IZO. The
thickness of the third metal layer 280c may be 50 .ANG. to 100
.ANG. (0.005 .mu.m to 0.01 .mu.m). In one embodiment, when the
thickness is less than 50 .ANG., the third layer 280c cannot be
evenly formed on the second metal layer 280b, and when the
thickness is more than 100 .ANG., an interference effect occurs,
lowering reflectivity by at least 10-15% especially in a blue
region, and the color of the transparent conductive oxide layer
itself is expressed.
[0039] Next, a photoresist pattern is formed on the third metal
layer 280c, and the first to third metal layers 280a to 280c are
blanket-etched by wet-etching using an etchant including at least
one of nitric acid, phosphoric acid or acetic acid, using the
photoresist pattern as a mask, to form a first electrode 280 made
of a sequential stack of the first to third metal layers 280a to
280c. Then, the photoresist pattern is removed using a stripping
solution.
[0040] Thus, the first electrode 280 including the first to third
metal layers 280a to 280c is completed.
[0041] A pixel defining layer 285 is formed on the first electrode
280 and patterned, thereby forming an opening 286. The pixel
defining layer 285 may be formed of one selected from the group
consisting of polyimide, benzocyclobutene series resin and
acrylate.
[0042] Then, an organic layer 290 including an organic emission
layer is formed in a region where the first electrode 280 is
exposed and on the pixel defining layer 285. The organic layer 290
may include one or a multi-layer of a hole injection layer, a hole
transport layer, a hole blocking layer, an electron transport layer
and an electron injection layer, in addition to the organic
emission layer.
[0043] A second electrode 300 is formed on substantially the entire
surface of the substrate including the organic layer 290. The
second electrode 300 may be formed of one metal selected from the
group consisting of Mg, Ag, Al, Ca and an alloy thereof. In other
embodiments, the second electrode 300 may be formed of a
transparent material such as ITO or IZO.
[0044] Thus, an organic light emitting display device formed in a
triple structure including the first electrode 280, the organic
layer 290 and the second electrode 300 is completed.
[0045] FIG. 3 illustrates a portable terminal 1 which is an
electronic device using an organic light emitting display device
according to an exemplary embodiment of the present invention.
[0046] Referring to FIG. 3, the portable terminal 1 includes an
organic light emitting display device 2. The portable terminal 1
also includes a body containing electronics, on which the organic
light emitting display device 2 is mounted. As described above, the
organic light emitting display device 2, in one embodiment, is
formed of a first electrode made of a sequential stack of Mo or an
Mo alloy, and Ag or an Ag alloy, and ITO, an organic layer
including an organic emission layer, and a second electrode,
stacked on a substrate in sequence. A thin film transistor, a
capacitor, a planarization layer, etc., are disposed between the
substrate and the first electrode. Here, the Mo or the Mo-alloy can
drastically decrease dark pixel defects by improving adhesion to
the planarization layer. Also, resistance of the first electrode
and its contact resistance to source and drain electrodes are
reduced, thereby reducing the driving voltage. A portable terminal
including such an organic light emitting display device has
improved display quality. Accordingly, the quality of the product
is improved.
[0047] While the above exemplary embodiment refers to a portable
terminal as an example of an electronic device, the organic light
emitting display device is not limited thereto and can be utilized
in various electronic devices.
[0048] The present invention will now be described with reference
to more specific exemplary embodiments, which are not intended to
limit the scope of the invention.
EXEMPLARY EMBODIMENT 1
[0049] An Mo layer was formed to a thickness of 200 .ANG. (0.02
.mu.m) on a substrate, an ATD layer, which is an Ag alloy layer
formed of ATD available from Hitachi, was formed to a thickness of
1000 .ANG. (0.1 .mu.m) on the Mo layer, and an ITO layer was formed
to a thickness of 70 .ANG. (0.007 .mu.m) on the ATD layer.
Subsequently, a photoresist pattern was formed on the ITO layer,
and the Mo layer, the ATD layer and the ITO layer were wet-etched
using the photoresist pattern as a mask so as to form a
reflection-type first electrode having a triple structure.
EXEMPLARY EMBODIMENT 2
[0050] An MoW alloy layer was formed to a thickness of 200 .ANG.
(0.02 .mu.m) on a substrate, an ATD layer, which is an Ag alloy
layer formed of ATD available from Hitachi, was formed to a
thickness of 1000 .ANG. (0.1 .mu.m) on the MoW alloy layer, and an
ITO layer was formed to a thickness of 70 .ANG. (0.007 .mu.m) on
the ATD layer. Subsequently, a photoresist pattern was formed on
the ITO layer, and the MoW alloy, the ATD layer and the ITO layer
were wet-etched using the photoresist pattern as a mask so as to
form a reflection-type first electrode having a triple
structure.
COMPARATIVE EXEMPLARY EMBODIMENT 1
[0051] An ITO layer was formed to a thickness of 200 .ANG. (0.02
.mu.m) on a substrate, an Ag layer was formed to a thickness of
1000 .ANG. (0.1 .mu.m) on the ITO layer, and an ITO layer was
formed to a thickness of 70 .ANG. (0.007 .mu.m) on the Ag layer.
This is the conventional structure of a first electrode.
[0052] Table 1 shows a comparison of resistivity between an organic
light emitting display device including the first electrode of
Comparative Exemplary Embodiment 1 and an organic light emitting
display device including the first electrode of Exemplary
Embodiment 1. TABLE-US-00001 TABLE 1 Lower ITO layer Lower Mo layer
of Comparative of Exemplary Exemplary Embodiment 1 Embodiment 1
Resistivity 160-180 .mu..OMEGA. cm 14-15 .mu..OMEGA. cm
[0053] Referring to Table 1, in Comparative Exemplary Embodiment 1,
the resistivity of the lower ITO layer constituting the first
electrode is about 160 to 180 .mu..OMEGA.cm, and in Exemplary
Embodiment 1, the resistivity of the lower Mo layer constituting
the first electrode is about 14 to 15 .mu..OMEGA.cm. Accordingly,
the resistivity of the Mo layer in Exemplary Embodiment 1 is
significantly lower than that of the lower ITO layer in Comparative
Exemplary Embodiment 1.
COMPARATIVE EXEMPLARY EMBODIMENT 2
[0054] An ITO layer was formed to a thickness of 200 .ANG. (0.02
.mu.m) on a substrate having a thin film transistor, an Ag layer
was formed to a thickness of 1000 .ANG. (0.1 .mu.m) on the ITO
layer, and an ITO layer was formed to a thickness of 70 .ANG.
(0.007 .mu.m) on the Ag layer. This is the conventional structure
of a first electrode.
[0055] Table 2 shows the comparison of contact resistance between
the first electrode of Comparative Exemplary Embodiment 2 and a
drain electrode (Ti/Al/Ti) of a thin film transistor, and between
the first electrode in Exemplary Embodiment 1 and a drain electrode
(Ti/Al/Ti) of a thin film transistor. TABLE-US-00002 TABLE 2
Comparative Exemplary Exemplary Embodiment 2 Embodiment 1 Contact
resistance 170 .OMEGA. 5.5 .OMEGA.
[0056] Referring to Table 2, contact resistance between the first
electrode and the drain electrode is 170 .OMEGA. in Comparative
Exemplary Embodiment 2 and 5.5 .OMEGA. in Exemplary Embodiment 1.
Accordingly, contact resistance in Exemplary Embodiment 1 is
significantly lower than that in Comparative Exemplary Embodiment
2.
[0057] FIG. 4A illustrates photographs of a first electrode
adhering to a substrate when the first electrode of Comparative
Exemplary Embodiment 1 is wet-etched, and FIG. 4B shows a
photograph of a first electrode adhering to a substrate when the
first electrode of Exemplary Embodiment 1 is wet-etched.
[0058] Referring to FIGS. 4A and 4B, A, B, C and D shown in the
photographs (a), (b) and (c) of FIG. 4A indicate unit pixels,
respectively. It can be seen in the photograph (a) of FIG. 4A that
a peeling off phenomenon occurs due to deterioration of adhesion
between a first electrode and a substrate, i.e., between an ITO
layer and a planarization layer, at unit pixel B. Also, it can be
noted that the peeling off phenomenon occurs at unit pixel C in the
photograph (b) of FIG. 4A, and additionally at unit pixel A in the
photograph (c) of FIG. 4A. In FIG. 4B, the peeling off phenomenon
does not occur, so it can be seen that adhesion between the
substrate and the first electrode of Exemplary Embodiment 1, i.e.,
between an Mo layer and a planarization layer, is excellent. In
FIGS. 4A and 4B, corresponding components are denoted by like
reference symbols.
[0059] FIG. 5 illustrates photographs (a) and (b) of dark pixel
defects caused by particles of an organic light emitting display
device including a first electrode of Comparative Exemplary
Embodiment 1. Since the first electrode of Comparative Exemplary
Embodiment 1 exhibits poor adhesion to a substrate, a very gentle
cleaning process is performed. In such instance, particles are not
completely removed, which is the main cause of dark pixel defects.
On the other hand, the first electrode of Exemplary Embodiment 1
exhibits good adhesion to a substrate, so that a strong cleaning
process can be performed. Thus, as particles are completely
removed, little or no dark pixel defects occur.
[0060] An organic light emitting display device according to an
exemplary embodiment of the present invention exhibits improved
adhesion to a planarization layer, which minimizes or reduces
defects such as dark pixels generated by particles, and reduces
resistance to source and drain electrodes compared to a
conventional organic light emitting display device, which minimizes
or reduces driving voltage. Also, a first electrode having a triple
structure is blanket-etched, thereby shortening process time and
simplifying a fabrication process.
[0061] Although the present invention has been described with
reference to certain exemplary embodiments thereof, it will be
understood by those skilled in the art that a variety of
modifications and variations may be made to the present invention
without departing from the spirit or scope of the present invention
defined in the appended claims, and their equivalents.
* * * * *